This application is based on application No. H11-362664 filed in Japan on Dec. 21, 1999, the entire contents of which are hereby incorporated by reference.
1. Field of the Invention
The present invention relates to an optical component produced by forming an anti-reflection film on a surface of a molding of a norbornene resin, and to a method for producing such an optical component.
2. Description of the Prior Art
In recent years, synthetic resins have come to be widely used as materials for optical components such as lenses, mirrors, and prisms. This is because synthetic resins are lighter and cheaper than glass materials, and can easily be molded into complex shapes. Conventionally preferred kinds of such synthetic resins are polymethyl methacrylate (PMMA) and polycarbonate (PC). However, both PMMA and PC are insufficiently heat resistant and in addition moisture-absorbent. Therefore, in practical use, moldings of those resins pose the serious problem of easily changing their shapes and refractive indices.
This has encouraged development of satisfactorily heat-resistant and non-moisture-absorbent synthetic resins, of which one outcome is norbornene resins having no polar group. Norbornene resins have proved to be excellent in transparency, heat resistance, and non-moisture-absorbency, and are thus effective as optical materials.
However, forming a conventional anti-reflection film on a molding of a norbornene resin results in rather low adherence between them, which inconveniently facilitates exfoliation of the anti-reflection film from the molding. The adherence declines particularly sharply at higher ambient temperatures and humidities and with greater film thicknesses. This has prompted attempts to improve the adherence of the anti-reflection film by adding a polar group to the norbornene resin. However, no satisfactory results are known to have been obtained to this date.
An object of the present invention is to provide an optical component having an anti-reflection film adhering to a surface of a molding of a norbornene resin so strongly as not to exfoliate therefrom, and to provide a method for producing such an optical component.
To achieve the above object, according to one aspect of the present invention, an optical component is provided with: a molding formed out of a material containing a norbornene resin having a polar group; and an anti-reflection film formed on a surface of the molding. This anti-reflection film is composed of, from the molding side to the air side: an equivalent film of which the overall refractive index as calculated according to formula (1) below is 1.52 to 1.8 and that includes, from the molding side to the air side, an intermediate layer measuring 10 to 50 nm in mechanical film thickness and containing Al2O3, a first high-refractive-index layer, and a first low-refractive-index layer containing SiO2 as a main ingredient,                     N        =                              n            g                    +                                    ∑                              i                =                1                            3                        ⁢                          xe2x80x83                        ⁢                          [                              4                ⁢                                  (                                                            n                      i                                        -                                          n                      g                                                        )                                ⁢                                  n                  i                                ⁢                                  n                  d                                            ]                                                          (        1        )            
where ng represents a refractive index of the molding and ni and di represent a refractive index and a mechanical film thickness, respectively, of an i-th layer of the equivalent film as counted from the molding side; a second high-refractive-index layer measuring 0.4xcex to 0.6xcex (where xcex is 480 to 550 nm) in optical film thickness and containing TiO2 as a main ingredient; and a second low-refractive-index layer measuring 0.2xcex to 0.3xcex (where xcex is 480 to 550 nm) in optical film thickness and containing SiO2 as a main ingredient.
According to another aspect of the present invention, an optical component is provided with: a molding formed out of a material containing a norbornene resin having a polar group; and an anti-reflection film formed on a surface of the molding. This anti-reflection film is composed of, from the molding side to the air side: a first high-refractive-index layer containing TiO2 as a main ingredient and formed with the molding heated to 70 to 130xc2x0 C.; a first low-refractive-index layer containing SiO2 as a main ingredient; a second high-refractive-index layer measuring 0.4xcex to 0.6xcex (where xcex is 480 to 550 nm) in optical film thickness and containing TiO2 as a main ingredient; and a second low-refractive-index layer measuring 0.2xcex to 0.3xcex (where xcex is 480 to 550 nm) in optical film thickness and containing SiO2 as a main ingredient.
In these optical components according to the present invention, an anti-reflection film composed of specifically defined layers is formed on a surface of a molding of a norbornene resin having a polar group. This ensures that the anti-reflection film adheres to the surface of the molding so strongly as not to exfoliate easily therefrom.
According to another aspect of the present invention, a method for producing an optical component includes: a molding step of forming a molding having a desired shape out of a material containing a norbornene resin having a polar group; a heating step of heating the molding to 70 to 130xc2x0 C.; and a vapor-deposition step of vapor-depositing an anti-reflection film as a first layer on a surface of the molding.
By this method according to the present invention, first a molding of a norbornene resin is heated to 70 to 130xc2x0 C., and then a first layer is vapor-deposited on the norbornene-resin molding. This ensures that an anti-reflection film adheres to the surface of the molding so strongly as not to exfoliate therefrom.